Modeling carbon sequestration in Mediterranean agroecosystems using the CAST model

This study evaluates soil organic carbon (SOC) sequestration in Mediterranean agroecosystems using the Carbon, Aggregation, and Structure Turnover (CAST) model, with a focus on agroecological and regenerative practices that support carbon farming (CF) strategies. Three case studies across Greece, Italy, and Spain were assessed to quantify SOC dynamics and carbon storage potential. In Koiliaris, Greece, avocado orchards adopting manure addition, mulching, and sustainable irrigation sequestered 3.81–4.71 tC/ha/yr between 2019 and 2024, with a projected decline to 1.15–1.50 tC/ha/yr by 2044 as SOC approaches saturation. In Lazio, Italy, regenerative olive groves accumulated 1.17 tC/ha/yr (2011–2025), slightly decreasing to 1.09 tC/ha/yr by 2045, indicating long-term SOC stability. In Sant Pau de Segúries, Spain, agroforestry systems gained 0.94 tC/ha/yr (2019–2024), increasing to 1.09 tC/ha/yr by 2044, whereas pastures showed SOC losses (−0.71 tC/ha/yr) due to forest-to-grassland conversion. SOC accumulation was predominantly associated with macro-aggregates (>250 μm) reflecting soil structural stability and resilience. The CAST model successfully simulated SOC turnover and aggregate fractions since the uncertainty of the simulation due to carbon input was low, demonstrating in this way its value for Monitoring, Reporting, and Verification (MRV) within CF schemes.